Stat Build: Put points in only 2 stats. Most builds like this in Rohan Online just put everything in psyche but I recommend putting some in Intelligence so that you have light pvp ability. You will have more than enough points in psyche to use Magic Barrier efficiently. Barring external influences, you should not be worried about running out of mana. Add some intelligence so that you could maximize Poison as well as other spells that are dependent on these two stats. However these psyche/intelligence skills are not in the build because you can only get them from skill stones off mobs or buy them from the cash shop.
PvE: If you can’t find a party, you’re better off finding solo quests and live off of those. However, because of the nature of the build, you will do yourself a favor if you just find a consistent party. The life of a healer isn’t very hard because all you need to do is keep track of life totals. You will be pmed like mad to join parties and you can get into some great boss farming parties and get some really great gears or items for synthesis.
PvP: Frankly, this build isn’t really build for one-on-one fights. Sure, you’re tough as nails with Magic Barrier and some damage reduction spells but you won’t be able to deal enough DoT damage and DPS to kill many people unless they screwed their build up. Priests really shine in group pvp to keep those tanks and DPS guys alive. The main focus in group pvp is to keep people alive.